Mohamed Osman Mohamud was duped in thinking he had a bomb to blow up people in the United States.

A Somali-American man has been found guilty of trying to bomb a Christmas tree lighting ceremony in the state of Oregon. Mohamed Osman Mohamud, 21, was given a fake bomb by undercover agents posing as Islamist militants, lawyers said. Mohamud was arrested after he tried to use his phone to detonate the fake car bomb near a crowded square in Portland. He will be sentenced on 14 May and may face a life sentence for attempting to use a weapon of mass destruction.

The Central Square in Portland was crowded with thousands of people attending the ceremony in December 2010 but the public was never in danger, authorities have said. But Mohamud’s lawyers argued that law enforcement officials had entrapped their client by inventing a crime. “We are disappointed with the verdict,” public defender Stephen Wax said, adding that he intended to appeal.

But the jury agreed with prosecutors that Mohamud, who was 19 years old at the time of arrest, could have pulled out of the plan at an earlier stage. He is reported to have told a friend on the day of the attempted bombing that it was “the greatest morning of my life”. The FBI said Mohamud made a “series of choices over a period of several years – choices that were leading him down a path that would have ended in violence. “His actions showed little regard for the rights and responsibilities that come with being an American or respect for the lives that he was prepared to take.”